Question

In ball mill, at which speed will there be centrifugation?

• A. \(\text{Operating}\)
• B. \(\text{Normal}\)
• C. \(\text{Critical}\)
• D. \(\text{Below normal}\)

Hint:

At critical speed in a ball mill, grinding media stay attached to the wall due to centrifugal force, preventing effective grinding.

Answer 1

The Correct Option is C

Step 1: Understanding ball mill operation.
- In a ball mill, the speed at which centrifugation occurs is called the critical speed, where centrifugal force overcomes gravitational force, causing the grinding media to stick to the mill wall.

Step 2: Explanation of incorrect options.
- (A) Operating speed: Generally lower than the critical speed and causes cascading of the grinding media.
- (B) Normal speed: Allows the media to cascade for grinding.
- (D) Below normal: Results in inefficient grinding as the media does not have sufficient motion.

Step 3: Selecting the correct option.
Since centrifugation occurs at critical speed, the correct answer is (C) Critical.